Traffic signal control system



Oct. 2, 1934.

'c. E. IVES 1,975,322

TRAFFIC SIGNAL CONTROL SYSTEM Filed May 6, 1926 2 Sheets-Sheet l Oct. 2, 1934. c. E. IVES TRAFFIC SIGNAL CONTROL SYSTEM Filed May 6, 1926 2 Sheets-Sheet 2 I??? I Z iffgrdfl' [1/55.

Patented Oct. 2, 1934 UITED STTES FFICE ATEN'E' 6 Claims.

My inventionrrelates to trafiic signal control systems and more particularly systems of the above character adapted for use incontrolling signals at street intersections throughout a controlled area and which may include a single street with a number of successive crossings, or a plurality of cross streets throughout the area to be controlled.

7 One of the features of my invention is the provision of a synchronizing control for a plurality of individual timer mechanisms, that is a means whereby the various timers may be brought back into synchronism or definite relation should theyleave such definiteor predetermined relation.

There are various features to my invention and these will be more particularly pointed out in the ensuing part of the specification and appended claims.

For a better understanding of my invention reference is to be had to the accompanying drawings, in which- Fig. 1 shows one form of my invention; and

Fig. 2 shows another arrangement incorporating my invention.-

Referring now more in detail to the system illustrated in Fig. l, I show a plurality of individual timber mechanism units T, T, etc. Three mechanisms are shown, but it is to be understood that any number may be used depending upon the area and number of intersections involved.

In the timer mechanisms shown individual driving elements are provided, that is a driving .magnet for each timer, and as illustrated the timer mechanisms are positioned at the intersection controlled thereby. However, if desired all of the timer mechanisms may be located at a central station and conductors extended to the corresponding intersection.

Referring more in detail to the timer mechanism T, and which corresponds to'the others although only shown in part, a main shaft 5 is provided carrying a driving ratchet 6 adapted to be advanced by the stepping magnet '7 so as to effect a continuous stepping advance of the timer shaft. A check pawl 8 is provided for preventing any return movement of the timer shaft.

Supported upon the rear end of the timer shaft are the cams for controlling the signal light contacts, the cam 10 being arranged for closing the contacts 11 for controlling the green or Go lamp G. This cam 10 is composed of two'sections which are relatively adjustable so as to vary the .period of lighting of the lamp G.

In the system illustrated a warning or change lamp Y is lighted with each change in the signal control lamps. Thus before the green lamp is extinguished due to the action of the cam 10 reaching the limit of its movement, the cam 12 closes the contact 13 tolight the yellow lamp Y. In the position of the apparatus as indi-v cated, both the yellow and green lamps are lighted, the cams 10 and 12- being shown in a position just before they pass off of the contact actuating wheels resting upon the periphery thereof. 7

After the green and yellow lamps are extinguished by the advance of earns 10 and 12, the cam 14 lifts its wheel to light the red lamp, which stays lighted during the advance of cam 14. During the lighting of the red lamp the yellow lamp is again lighted to indicate the next change in signals when the cam 15 comes around to close its corresponding wheel and contacts. I

The timing of the signal lamps may be varied by the adjustment of the hands 1617 on the face of the dial 18. That is, these hands 16 and 1'7 may be adjusted around to various relative positions on the dial 18 and thus correspondingly adjust the cams. Thereby the red and green lamps are lighted and effaced accordingly so that they are on and off for diiferent periods during the cycle or rotation of the timer shaft.

In the system as illustrated in Fig. 1, the various timers are driven from a common impulse source furnished from an impulse device l driven by a motor M through a variable drive V. Thus the speed of the impulses may be varied by adjusting the drive V whichis diagrammatically illustrated as a well known Reeves drive. It will thus be seen that the common impulse or driving circuit will drive all of the timers in synchronism, advancing them in a certain definite relation. This, of course, is desirable in that these timers are set to operate the signals at successive crossings at definite times, either by progressive lightv ing so as to give a coordinate trafific control, or they may operate simultaneously. However, irrespective of the character of traffic movement, it is essential that the timers operate in synchronism, or in other words all of the individual timer mechanism units continue to advance in a predetermined definite relations With the timers electrically driven and without any mechanical connection between them to hold them in this definite relationship, they may become out of step or said definite relationship for various reasons, such as byv an occasional failure of the.step-.

ping or driving magnet of one or more of the timers. In such case one or more of the timers may lag behind the others and thus throw them all out of their predetermined. relationship.

To overcome this objection I have provided socalled synchronizing mechanism for positively returning said timers into said predetermined definite relation should any of them drop out of synchronism with the rest.

To this end I provide a magnetic synchronizing device to the timer shaft of each unit, this being in the form of a field magnet 20 and armature 21, the latter being carried with the timer shaft. A synchronizing current is supplied to this device, and of course to all others in the system, at definite times so that should any one or more of the timers be out of position they will be. drawn back into positive definite relation. To thisend I preferably provide a synchronizing circuit controlled from each of the timers through a pair of contacts 22 carried upon the timer shaft. Thus each timer acts as a synchronizing device for the entire system. These control contacts 22 are all connected to the common synchronizing or interlocking conductor S. The synchronizing current may be provided from any suitable source and I show a common current feed conductor 23 which is connected with the power generator P and extends to all of the timer units through the contacts 22 thereof. Thus when a contact 22 is closed current flows from the power conductor 23 through the closed contacts 22, the winding of armature 21 to collector ring 24, continuing on through the winding of the field'magnet 20 to the common return 24 back to the-generator P.

This current which flows through contacts 22 before it reaches the windingof armature 21 divides at point 25 and part of the current ex tending through the collector ring 26 and out over conductor 27 to the common synchronizing conductor S from which it flows through the synchronizing magnets of all the timers and brings those which are lagging behind up into step with the rest.

Referring now more in detail to the system of Fig.1, and assuming that the various timers are .in the positions indicated, that is, with the timers T and T in a so-called normal condition as indicated by the zero arrow on the dial, and with the timer T in a retarded or lagging position. That is, it is assumed that the timer T has fallen. behind and is out of synchronism or definite relation with the othertimers. Accordingly when the timers T and T reach their normal position, their contacts 22 close. Taking the lower timer T for example, upon closure of contacts 22 a. synchronizing circuit is established and a synchronizing impulse or current connected with the common synchronizing conductor S. This circuit is traced from the live pole of generator P, along conductor 23 to upper contact 22 of timer T to point 25 where the current divides, part of it flowing through collector ring 26, its brush and conductor 29 to synchronizing conductor S. The said current also flows from the common point 25 through the winding of armature 21 of T collector ring 24 and the winding of field magnet 20 to'the rear conductor 24, energizing the synchronizing device of T However, at this time this has no effect, because the timer is in a normal position. However, the current flowing" to the synchronizing conductor S extends up to the timer T and acts upon its synchronizing magnet to bring the timer '1 to normal and in step with the other timers. This synchronizing circuit at timer T is traced from the conductor S through conductor 29, ring 26 to point 25, winding of armature 21, ring 24 and the winding of field magnet 20, back to the common return 24. Thus the armature and field magnets of the synchronizing device of timer T are energized to draw the timer around into a normal or synchronized position so that it is in its proper position relative to the other timers and they are therefore all in step.

It will be seen that when contact 22 of timer T closed, the contact 22 of timer T also closed, because both of these timers are in step. This simply sends impulses out over the conductor S in common and thereby all timers that are retarded are brought up to a normal or synchronized position. Any timers that have their shafts advanced beyond a synchronized position, cannot be drawn backwardly because of the retaining pawl 8. It will be seen though, that when any timer falls back out of step with the rest it is automatically drawn to normal-or synchronized position with the rest when a contact 22 closes. In this way each timer is a synchronized setting device for the rest. Thus the various timers are more readily maintained in definite relationship. Although I have shown this synchronizing circuit as controlled'by all of the timers, it is apparent that one alone may be used if desired. Also, :although I have shown a specific form of synchronizing mechanism, it is to be understood that I contemplate employing other deviceaxdepending upon the timer mechanism employed and other conditions.

Referring now more in detail to the operation of the system shown in Fig. 2, this has the syn-. chroniz-ing mechanism-applied to each of the timers, the same as in'Fig. 1, except for the necessary difference in circuit control. In Fig. 2 the system is so arranged that I am enabled to vary the time of the cycle, that-is the periodof operation of the cycle, and also vary the'periodof operation of the yellow or warning signal Y.

In Fig. 2 I have shown the three timer units T, T, and T although it is to be'iunderstood that any number of timers may be connected into the system, depending upon the number of intersections or extent of the area controlled. The three timers are all of the same construction,- although the upper one only is shown complete. The cycle timer shaft 5 is driven by the stepping magnet 7 and said shaft carries. a.v plurality of contact discs for controlling the synchronizing magnet SM and the warning light control device W. The latter device is actuated by a's'uitable driving element preferably in the form of a stepping magnet 40 which receives its stepping impulses from the impulse device 39 controlled by the motor M through the variable Reeves drive V, this constituting the power drive for the variable warning light control W.

In general it might be stated that the cycle shaft 5 of the timer is continually advancing through action of the motor magnet 7 and for each cycle or complete revolution of the timer shaft 5 the warning drive W receives two half revolution advances. In other words, each time a pointer, as 16 or 17, of the timer dial passes the normal pointer above the dial, a circuit is closed for the stepping magnet 40 of W, so as'to effect a half revolution advance of the. shaft 42. For one half revolution of shaft 42 the contact drums carried thereby light the green light and a short period for the yellow light as a warning change, and for the other half revolution of shaft 42 the red lamp is lighted with a short period of operation for the yellow light.

In the present form of my invention the synchronizing is done by magnet SM as before, and the circuit therefor is closed by contacts 22, which are shown in the form of a drum and brush arrangement.

The timer T in Fig. 2 is shown as several steps behind the timers T and T thus corresponding to the position of the timers in Fig. 1. Therefore assuming that the timers of Fig. 2 are advancing in the order illustrated, when contacts 22 of timerT are closed, synchronizing impulse is sent out over the common synchronizing conductor S to synchronize timers out of step. This circuit also flows through the magnets SM of timers T and T but without eifect because these two timers are in proper position. This synchronizing impulse also flows through the magnet SM of timer T, but this timer being out of proper position is drawn up into synchronism with the other timers. This circuit for the magnet SM of timer T is established from P, through 39, conductor 46, ring 45 and contacts 22 of T conductor S, conductor 43 of T, winding of magnet 20, brush and ring 24, the winding of armature 21, brush and ring 26, to the common return 24. This circuit for device SM of T draws the armature 21 into alinement with the field magnet 20 and thus all of the timers are brought back into synchronism or definite relation. It will thus be seen that each timer may act to synchronize the rest of the system.

Now as to the signal lamp control and referring to the contact rings on the cycle timer shaft 5, the shaded portions on the four rings indicate the current carrying sections, and these are all connected in common to the last ring 45 which is the current carrying ring because of its connection to the impulse conductor 46 connected to the warning lamp drive 39. Assuming that the timer T is advancing from the position indicated in Fig. 2, and that the warning drive W is in the position shown. Under this condition the green lamp G is lighted through connection with ring 4'7, the shaded part of which represents current carrying conductor and is connected with the outer ring 48 connected to the return side of the current source 49. This is shown as a separate source from the generator P, although it may be the same if desired.

As soon as the contact segment 50 of the cycle drum reaches its brush it supplies current from the impulse conductor 46 to the ring 45, and then on to segment 50 and its brush 51. The current impulses then flow on through the brushes and rings of drum 48 to the steppi magnet 40 which advances the shaft 42 a half revolution. During this advance the yellow lamp Y is momentarily lighted as an indication of change in traffic and then the green and yellow lamp simultaneously extinguished. The red lamp R is then lighted just before the drum W comes to rest on its half revolution. The drum W now remains inert until the cycle drum brings its ring 53 to engage its brush 54, thereby again furnishing a stepping circuit for the magnet 40 of the warning drive W so that it is again rotated for a half revolution to correspondingly shift the lamps. These sections 50 and 53 on the cycle drum are sufiiciently long to supply impulses to the magnet 40 to complete a half revolution of the drum W each time.

It will thus be seen that for each revolution or cycle of the timer shaft 5 the warning drum W receives two half revolutions, each time shifting the traffic signal lamps R and G and also momentarily lighting the warning change lamp Y.

The rings carrying the contact segments 50 and 53 are adjusted by the hands 16 and 17, the same as the adjustment of the cams on the timer shaft of Fig. 1. That is by adjusting the hands 16 and 17 on the dial the contact rings 50 and 53 are correspondingly adjusted upon the shaft 5, so as to give any desired timing for the lamps.

With the system shown in Fig. 2 I am enabled to vary the time of the cycle without varying the time or period of lighting of the warning change light Y. That is, assuming that the time of the cycle is to be changed, but the time of lighting of the warning lamp maintained constant, I adjust the variable drive V, thus changing the speed of the impulses and thereby the speed of the timer shaft 5. This, however, does not affect the warning drive shaft 42 because it receives its advance through the magnet 40 which receives its driving impulses from the impulse device 39. Should it be desired to change the period of lighting of the warning lamp, this may be done by adjusting the variable drive V so as to increase or decrease the speed of the impulses from device 39.

It will thus be seen that in the system of Fig. 2 I am enabled to vary the time of the cycle without changing the period of lighting of the warning lamp, or vice versa, or change both.

At the same time although separate driving elements are provided for each of the timers, by the synchronizing mechanism employed I am enabled to bring all of the devices back into definite relation should any one or more of them fall behind or advance, such as might occur.

For a more complete reference of the manner in which the timer segments may be adjusted,

reference may be had. to my patent, Serial No.

166,677, filed May 4, 1926, Patent No. 1,931,350.

What I claim as new and desire to secure by United States Letters Patent is:

1. In a control system, a plurality of shafts, means for driving said shafts substantially in unison, an armature carried by each shaft, a field magnet for each armature disposed in operable relationship thereto, a winding on each armature and field magnet, a plurality of pairs of cooperating contact members one of each pair carried by one of said shafts, and a circuit including a source of electrical energy, all of the armature and field coil windings and all of said pairs of contacts, connected in a manner whereby on engagement of any one of said pairs of said contacts all of said armature coils and field coils will be energized to turn the shafts to the same exact position.

2. A combination defined in claim 1 wherein said circuit includes a pair of slip rings and conv tact brushes carried by the shafts, whereby current may be supplied to said coils at any shaft position.

3. An electric control system including a plurality of shafts, a motor magnet for each shaft. a I

common source of current for operating the motor magnets and driving the shafts in unison in fixed relation, a synchronizing armature on each shaft and a field magnet therefor, a pair of contacts for each shaft with all the contact pairs closed simultaneously when the shafts are in fixed relation, and a synchronizing circuit common to all said armatures and magnets and closed by any contact pair closing in advance of the contacts associated with any shaft which is out of fixed relation to the shaft of said closing contact pair, for restoring said shafts into synchronism if they leave said fixed relation.

4. An electric control system including a plurality of shafts, a driving element for each shaft, a driving circuit for operating all said elements to advance the shafts in definite relation, a synchronizing conductor common to all the shafts, a synchronizing magnet for each shaft operated over said conductor, all of said magnets being multiply connected to said conductor, an electromagnetic armature for each synchronizing magnet coupled to the corresponding shaft, a pair of contacts for each shaft, means for operating said pair of contacts at a predetermined position of its corresponding shaft, and control means for transmitting a synchronizing current over said conductor should the shafts become out of definite relation, responsive to operation of the first oflsaid pair of contacts which reaches said predetermined position whereby said armature and magnets may restore the shafts to said definite relation.

5. An electric control system including a plurality of shafts, an electrically operated driving element for each shaft, means for operating said elements to advance the shafts in definite relation to each other, a synchronizing mechanism for each shaft including anelectromagnet and cooperating magnetic structure for each shaft to set the shaft in a predetermined position, a pair of contacts for each shaft closed responsive to the shaft each time it reaches said predetermined position, and means responsive to closure of a pair of said contacts for energizing the electromagnets of the shafts out of step to cause their magnets and their cooperating magnetic structure to align whereby the said definite relation between shafts is restored.

6. An electric control system including a plurality of shafts, means including a common source of energy for rotating said shafts in unison, a field magnet surrounding each of said shafts and an armature carri d by each shaft to be aligned with its shaft to a predetermined position by its corresponding magnet When the latter is energized, means normally inoperative, including all of said magnets for energizing them, and means responsive to the first of said shafts to reach said predetermined position to render said normally inoperative means operative, so that should any of said shafts get out of said relation it will he turned by its own armature to said predetermined position.

CLIFFORD E. IVES. 

